This invention refers to a device for measuring the flow-rate of a fluid along a conduit, as well as regards a digital flow-meter comprising the aforementioned measuring device combined with an optical flow-rate detecting and reading system.
Several measuring devices are currently known by which it is possible to provide a visual indication of the flow-rate of a fluid flowing along a measuring tubular element, in which the flow-rate value is directly read on a flow-meter in respect to the position of a float visible through a suitable window, or by mechanical, magnetic or electrical detection to be read on a proper dial of an electronic reading instrument.
Float-type systems are widely diffused, in that they are easily installable and are of relatively low cost; nevertheless, they present the serious drawback of providing a somewhat imprecise measurement of the flow-rate, as well as being difficult to read in presence of a turbid fluid or due to a possible deposition of lime on the window for displaying the float.
While on one hand mechanical-type flow-meters provide a sufficiently precise measurement of the flow rate, nevertheless they are extremely complex in structure, and subject to wear problems, as well as allow only an in situ reading of the flow-rate without any possibility of transferring the detected data to remote positions or of managing the information.
There are also electric, magnetic or ultrasound-type of flow-rate measuring devices which require sophisticated technologies and the use of probes or electrical and/or magnetic components designed to come into contact with metal parts, while a fluid or a gas is flowing along a measuring pipe. Flow-meters of this kind are known for example by U.S. Pat. Nos. 6,189,389 issued Feb. 20, 2001 to Jan Aart van Bekkum and Vladimir Smychliaev for xe2x80x9cUltrasonic Flowmeterxe2x80x9d; U.S. Pat. No. 6,170,338 issued Jan. 9, 2001 to Lowell A. Kleven, et al. for xe2x80x9cVortex Flowmeter with Signal Processingxe2x80x9d; and U.S. Pat. No. 4,611,105 issued Sep. 9, 1986 to Klaus Kobold for xe2x80x9cDevice for the Measurement of Through-Flow with Potential-Free End Contact Switchxe2x80x9d.
Besides being structurally complex and relatively expensive, in that the various electric and/or magnetic members for measuring the flow-rate constitute an integral part of the same flow-meter, these types of flow-meters also involve some drawbacks, due to induced currents, eddy currents, or external magnetic fields which tend to negatively influence the measurement of the flow-rate.
A first object of this invention is to provide a tubular flow-meter device for measuring the flow-rate of a fluid, liquid or gas, which can be permanently associated with a duct or circulation system for the fluid, and which can be used in combination with an electronic apparatus, made as a separate part, for detecting and measuring the flow-rate.
A second object of this invention is to provide a digital flow-meter capable of obviating the drawbacks of previously known flow-meters, comprising the aforementioned tubular measuring device, combined with an electronic flow detecting apparatus provided with an optical flow-sensing system which is wholly devoid of negative external influences, extremely economical and easily installable.
In this way, an operator, having a single reading instrument, can measure the flow in different points of a single circulation system for the fluid or in different systems, in which a tubular measuring device according to the invention has been installed.
In general, according to a first aspect of the invention, a tubular device for measuring the flow-rate of a fluid along a duct, has been provided, the device comprising:
an outer tubular body provided with an inlet pipe fitting and an outlet pipe fitting for the fluid;
a tubular element, made of transparent plastic material, which sealingly extends inside the outer tubular body, between the aforesaid inlet and outlet pipe fittings;
said outer tubular body being provided on opposite sides with openings for seating, respectively, a light-emitting element and a light-receiving element facing each other;
an axially slidable light-shuttering member entrained by the flow within the inner tubular element, said light-shuttering member being shaped to partialize the light beam between the light-emitting element and the light-receiving element to provide an electric signal proportional to the flow-rate; and
a biasing spring member acting on the light-shuttering member to balance the thrust exerted by the fluid flowing along said inner tubular element.
According to another aspect of the invention, an electronic flow-meter device has been provided, comprising an apparatus for sensing and measuring the flow-rate, in combination with the aforementioned tubular measuring device, in which the light emitter and light receiver are removably disposable into opposed side openings in the outer tubular body of the measuring device, and in which the light emitter and light receiver are connected to an electronic control unit designed to provide a digital indication of the flow-rate.